1. Field of the Invention
The present invention is concerned with the presence of certain agents in a toilet detergent tablet having an acyl isethionate as the predominant surface active detergent, to lessen the tendency of the tablet to form mush in the holder.
It is well known that toilet tablets, both those based on soap and on nonsoap synthetic detergents, absorb water, or hydrate, when left wet in the conventional holder, or dish, after using. The hydrate is soft, and this condition may exist not only on the surface but for some distance below the surface. The hydrate falls from the tablet, or is removed during the next usage, depending upon the degree of softness. This softening and removal is variously referred to as sliming, sloughing, melting, slushing, smearing, slopping mushing, etc.
Various additives have been incorporated in soap and detergent tablets to ameliorate mushing tendencies, as set forth elsewhere herein. However, it is believed that the anti-mushing agents of the present invention have particular adaptability to nonsoap detergent toilet tablets wherein an acyl isethionate is the predominant surface-active agent.
2. The Prior Art
The most pertinent art known to applicant is set forth below.
A lithium salt of the linoleic dimer acid is disclosed as a lubricant component in U.S. Pat. No. 2,983,680. U.S. Pat. No. 3,267,038 discloses linoleic dimer acid and related polymeric acids as corrosion inhibitors in detergent compositions containing a polyphosphate. U.S. Pat. No. 3,538,009 discloses the use of linoleic dimer acid and related polymeric acids in detergent compositions to reduce skin irritation.
Sodium sulfate is a by-product formed in the manufacture of substantially all sulfate and sulfonate detergents. Representative patents disclosing or suggesting the presence of sodium sulfate in detergent tablets are U.S. Pat. Nos. 2,846,398, 3,055,837, and 3,383,320.
The use of sodium chloride, both with and without sodium sulfate, is known in toilet tablets as disclosed in the following representative patents.
Mixtures of potassium sulfate and potassium chloride in a nonsoap aerated tablet are shown in U.S. Pat. No. 2,407,647. In this patent there is disclosed a nonsoap aerated tablet having 1.5 to 10.5 percent total K.sub.2 SO.sub.4 and KCl in the ratio 1:2.
U.S. Pat. No. 2,356,903 discloses a nonsoap tablet containing 5 to 40 percent of finely divided NaCl or KCl. It is disclosed in this patent that powdered sodium sulfate increases the tendency of the tablet to become smeary on the washstand, and that sodium sulfate or sodium chloride decreases this tendency.
U.S. Pat. No. 2,686,761 discloses milled soap having 35-40 percent water and 1-12 percent sodium chloride.
Mixtures of sodium sulfate and sodium chloride in a detergent having a liquid and a particulate form are disclosed in the ratio of 5.38 and 0.83 in U.S. Pat. No. 2,744,874. Sodium sulfate and sodium chloride at a combined level of 1 to 5 percent and a ratio of 4.87 to 0.20, tablet basis, are disclosed in U.S. Pat. No. 2,991,253.
U.S. Pat. No. 3,055,837 discloses that sodium chloride may be present as a filler in a detergent tablet and U.S. Pat. No. 3,070,547 discloses that the presence of alkali-metal chlorides in a soap-synthetic tablet reduces smear or slushiness thereof, and further discloses that the effectiveness of the alkali-metal sulfates in this respect is only about one-half that of the chlorides.
U.S. Pat. No. 3,223,645 discloses 2-16 percent of a mixture of sodium chloride and potassium chloride in a soap tablet.
U.S. Pat. No. 3,247,121 discloses a soap-synthetic tablet with 0-85 percent synthetic detergent; 0.5-30 percent alpha-sulfo soap to lessen smear; 0-15 percent free fatty acids; 2-12 percent inorganic salts to firm the tablet and to aid in preventing undesirable smear without unacceptable surface crystallization; and 0-15 percent water.
U.S. Pat. No. 3,376,229 relates to the use of a firming agent in a synthetic detergent tablet based mainly on acyl isethionates, the firming agent being unesterified alkali-metal salts of isethionic acid, employed in amounts in excess of that associated with the acyl isethionate detergent.
U.S. Pat. No. 3,576,749 teaches that 1-3 percent sodium chloride provides acceptable smear characteristics when incorporated in a soap tablet free from nonsoap detergents.
South African application No. 63/3067 discloses a synthetic detergent tablet containing from about 46 to about 88 percent of inorganic alkaline and neutral salts, among which are sulfates and chlorides.
The procedures for preparing alkali metal acyl isethionates are well known to those skilled in the art. The reaction between isethionic acid free of its salts, and fatty acids is described in U.S. Pat. No. 3,151,136. The acid reaction product is neutralized preferably with a mixture of sodium hydroxide and sodium disilicate. U.S. Pat. No. 3,320,292 discloses the use of a basic zinc compound as a catalyst in the preparation of an acyl isethionate from a fatty acid and sodium isethionate, while U.S. Pat. No. 3,383,396 discloses the use of a zirconium compound in the same preparation. U.S. Pat. No. 3,376,229 describes the use of about 4 to 7 percent free sodium isethionate to harden a detergent bar having a composition in accordance with the instant invention, except for the anti-mushing additives. The basic bar composition is described in U.S. Patent No. 2,894,912. U.S. Pat. Nos. 3,420,857 and 3,420,858 disclose processes for controlling the distribution of the several chain-length fatty acids used in the admixture in the preparation of acyl isethionates. U.S. Pat. No. 3,429,136 discloses a step of flash-cooling acyl isethionates after preparation.